TY - JOUR
T1 - Sex beyond the genitalia: The human brain mosaic
JF - Proceedings of the National Academy of Sciences
JO - Proc Natl Acad Sci USA
SP - 15468
LP - 15473
DO - 10.1073/pnas.1509654112
VL - 112
IS - 50
AU - Joel, Daphna
AU - Berman, Zohar
AU - Tavor, Ido
AU - Wexler, Nadav
AU - Gaber, Olga
AU - Stein, Yaniv
AU - Shefi, Nisan
AU - Pool, Jared
AU - Urchs, Sebastian
AU - Margulies, Daniel S.
AU - Liem, Franziskus
AU - Hänggi, Jürgen
AU - Jäncke, Lutz
AU - Assaf, Yaniv
Y1 - 2015/12/15
UR - http://www.pnas.org/content/112/50/15468.abstract
N2 - Sex/gender differences in the brain are of high social interest because their presence is typically assumed to prove that humans belong to two distinct categories not only in terms of their genitalia, and thus justify differential treatment of males and females. Here we show that, although there are sex/gender differences in brain and behavior, humans and human brains are comprised of unique “mosaics” of features, some more common in females compared with males, some more common in males compared with females, and some common in both females and males. Our results demonstrate that regardless of the cause of observed sex/gender differences in brain and behavior (nature or nurture), human brains cannot be categorized into two distinct classes: male brain/female brain.Whereas a categorical difference in the genitals has always been acknowledged, the question of how far these categories extend into human biology is still not resolved. Documented sex/gender differences in the brain are often taken as support of a sexually dimorphic view of human brains (“female brain” or “male brain”). However, such a distinction would be possible only if sex/gender differences in brain features were highly dimorphic (i.e., little overlap between the forms of these features in males and females) and internally consistent (i.e., a brain has only “male” or only “female” features). Here, analysis of MRIs of more than 1,400 human brains from four datasets reveals extensive overlap between the distributions of females and males for all gray matter, white matter, and connections assessed. Moreover, analyses of internal consistency reveal that brains with features that are consistently at one end of the “maleness-femaleness” continuum are rare. Rather, most brains are comprised of unique “mosaics” of features, some more common in females compared with males, some more common in males compared with females, and some common in both females and males. Our findings are robust across sample, age, type of MRI, and method of analysis. These findings are corroborated by a similar analysis of personality traits, attitudes, interests, and behaviors of more than 5,500 individuals, which reveals that internal consistency is extremely rare. Our study demonstrates that, although there are sex/gender differences in the brain, human brains do not belong to one of two distinct categories: male brain/female brain.
ER -